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This is an example where for one bib record there are several items. One of the items is also linked to a different bib. So instead of creating a new instance record for the same item and having the item info in two different instance records (1 for the bib and 1 for the analytic bib), we can record the analytic information as part of the attributes on the item (refer to line # # 80)
6. EBook
This represents instance record for an ebook. The URI information is recorded at the holdings level and doesn't have to be recorded at the item level.